32186 datasheet(533/1032 Pages) RENESAS

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A/D CONVERTER

11-35

32185/32186 Group Hardware Manual

Rev.1.10 REJ09B0235-0110 May 15, 07

11.3 Functional Description of A/D Converter

11.3.1 How to Find Analog Input Voltages

The A/D Converter performs A/D conversion using a 10-bit successive approximation method. The equa-

tion shown below is used to calculate the actual analog input voltage from the digital value obtained by

executing A/D conversion.

Analog input voltage [v] =

A/D conversion result x VREF input voltage [V]

1,024

The A/D Converter is a 10-bit converter, providing a resolution of 1,024 discrete voltage levels. Because

the reference voltage for the A/D Converter is the voltage applied to the VREF0 pin, make sure that an

exact and stable constant-voltage power supply is connected to VREF0. Also make sure the analog circuit

power supply and ground (AVCC0, AVSS0) are separated from those of the digital circuit, with sufficient

noise prevention measures incorporated.

For details about the conversion accuracy, see Section 11.3.5, “Accuracy of A/D Conversion.”

11.3 Functional Description of A/D Converter

Figure 11.3.1 Outline Block Diagram of the Successive Approximation-type A/D Converter Unit

ADiIN0

ADiIN1

ADiIN2

ADiIN3

ADiIN4

ADiIN5

ADiIN6

ADiIN7

Selector

AVSSi

VREFi

10-bit A/Di Successive

Approximation Register

(ADiSAR)

10-bit

A/Di Data Register

A/Di Comparate

Data Register

A/D Control Circuit

10-bit D/A Converter

Comparator

ADiIN8

ADiIN9

ADiIN10

ADiIN11

ADiIN12

ADiIN13

ADiIN14

ADiIN15

ADiCMP

ADiDT0–15

Successive Approximation-type

A/D Converter Unit

AVCCi

Vref

VIN

Sample-and-Hold

Control Circuit

i=0

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